CN1934714A - Organic semiconductor element and organic el display device using the same - Google Patents

Abstract

An organic semiconductor element provided with an FET having a structure that can control a channel length short and prevents contact resistance due to a step part from increasing, and a high aperture ratio organic light emitting display device using the organic FET. On a substrate (1), a first conductive layer (2) is provided as one of source/drain electrodes, and on the first conductive layer (2), an organic semiconductor layer (3) and a second conductive layer (4) to be the other of the source/drain electrodes are provided. Then, on a side plane of the organic semiconductor layer or a front plane of the semiconductor layer (3) exposed by removing a part of the second conductive layer, and on a side plane of the second conductive layer, a gate electrode (third conductive layer) (6) is provided through an insulating layer (5) to form the FET. The organic semiconductor element is provided with the FET. The organic EL display device has the FET having such structure stacked on an organic EL part as a drive element.

Description

Organic semiconductor element and organic EL display device using the same

technical field

The present invention relates to an organic semiconductor element including a field effect transistor (hereinafter referred to as FET) using an organic semiconductor, and an organic EL display device using the organic semiconductor element. More specifically, it relates to an organic semiconductor element that uses an organic semiconductor, but can make the channel length very short, and can constitute a display device only by laminating with an organic EL part, and an organic EL display device using the organic semiconductor element. .

Background technique

A known conventional FET structure using an organic semiconductor layer is the structure shown in FIGS. 9A to 9C . That is, the structure shown in FIG. 9A is called a bottom contact (bottom contact) (BC) type, for example, on an insulating film 32 on a gate electrode 31 made of a silicon substrate, a pair of source electrode/drain electrode is provided. 33 and 34, and the organic semiconductor layer 35 is provided on the surface thereof, whereby the organic semiconductor layer 35 between the source/drain electrodes 33 and 34 is used as a channel region. Since this structure can form the source/drain electrodes 33, 34 using photolithography technology, it can be formed with a certain degree of fine pattern, but since the organic semiconductor layer 35 is provided on the source electrode/drain electrode step difference Therefore, the coverage of the organic semiconductor layer 35 deteriorates, and a void 36 is easily formed between the organic semiconductor layer 35 as a channel region and the corners of the bottom surfaces of both electrodes 33, 34, resulting in an increase in contact resistance.

In addition, the structure shown in FIG. 9B is called a top contact (TC) type, an organic semiconductor layer 35 is provided on an insulating film 32 on a gate electrode 31, and a source electrode/drain is formed thereon. The electrode electrodes 33 , 34 , and thus, the organic semiconductor layer 35 located under the source/drain electrodes 33 , 34 serves as a channel region. This structure does not have a problem with the coverage of the organic semiconductor layer 35 , but after the formation of the organic semiconductor layer 35 , it is necessary to form electrodes. However, the organic semiconductor material cannot be patterned by photolithography by exposing it to a solvent or an aqueous alkali solution, and it is necessary to use a shadow mask (metal mask) made of a metal plate to form the organic semiconductor layer 35 . The resolution of the shadow mask is 25 μm, and fine patterns cannot be formed, and there is a problem that the channel length cannot be shortened.

In addition, the structure shown in FIG. 9C is called a top and bottom contact (top and bottom contact) (TBC) type, and one side 33 of the source electrode/drain electrode is provided on a part of the insulating film 32, and exposed thereon. The organic semiconductor layer 35 is provided on the insulating film 32, and the other side 34 of the source electrode/drain electrode is provided thereon, so that the side surface of the side 33 of the source electrode/drain electrode and the step of the other side 34 The organic semiconductor layer 35 between the difference portions serves as a channel region (for example, refer to Patent Document 1). In this structure, since the channel length can be controlled by the thickness of the organic semiconductor layer 35, it is easy to shorten the channel length. Since the organic semiconductor layer is used, there is a problem that the coverage thereof deteriorates and the contact resistance increases.

Patent Document 1: Japanese Unexamined Patent Publication No. 2003-258265 (for example, FIG. 4 )

Contents of the invention

As mentioned above, in conventional FETs using organic semiconductors, the coverage rate deteriorates when there is a step difference in the organic layer, so the contact resistance increases, and it is impossible to form a fine source if a flat organic semiconductor layer is used. electrode/drain electrode, so the channel length cannot be shortened, and there is a problem that no matter which structure is used, a low-resistance channel cannot be formed.

In addition, due to this situation, for example, in an active display device using an organic EL semiconductor, an organic semiconductor element cannot be used as the driving element, but a silicon-based semiconductor such as polysilicon is used as the driving element. Therefore, both organic semiconductors and silicon-based semiconductors must be used. In addition, in the case of using a silicon-based semiconductor to form a driving element, it is necessary to use photolithography technology. However, as mentioned above, photolithography technology cannot be used after forming an organic semiconductor film, so it cannot be formed on the organic EL part. drive element. On the other hand, when the drive element is formed on the substrate side, it is necessary to take in light from the surface side, and therefore, the electrodes disposed on the upper part must be light-transmitting electrodes. On the other hand, high-temperature heat treatment cannot be performed after the organic EL semiconductor layer is laminated. However, low-resistance light-transmitting electrodes generally require high-temperature treatment, so they cannot be formed on the surface side. Therefore, as shown in the plan explanatory diagram of FIG. 5D described later, the light emitting part L and the driving element part (Tr and capacitor CAPA) must be separately formed on a plane, and the area of the display part becomes smaller and the aperture ratio (aperture ratio) becomes smaller. Lowering the problem.

The present invention was made to solve the above problems, and an object of the present invention is to provide an organic semiconductor element of an FET having a structure capable of controlling the channel length to be small and not causing an increase in contact resistance due to a step portion.

Another object of the present invention is to provide an organic EL display device, which uses an organic semiconductor layer as the semiconductor layer to constitute an active organic light-emitting display device, and forms a light-emitting part, a driving element, and a capacitor part into a stacked structure, A display portion with a large aperture ratio can be formed.

The organic semiconductor element of the present invention has a FET, and the FET includes: a substrate; a first conductive layer provided on the substrate as a source electrode/drain electrode; an organic semiconductor layer provided on the first conductive layer; The other second conductive layer as the source electrode/drain electrode provided on the organic semiconductor layer; the side surface of the organic semiconductor layer or the surface of the organic semiconductor layer exposed by removing a part of the second conductive layer and the side surface of the second conductive layer, and a gate electrode provided via an insulating layer.

By providing an organic semiconductor layer lowering the energy barrier between the above-mentioned first conductive layer and the organic semiconductor layer and/or between the above-mentioned second conductive layer and the above-mentioned organic semiconductor layer, it is possible to easily operate at a low operating voltage. Under flow current, so preferred. The structure of the present invention is a structure in which the organic semiconductor layer is sandwiched by the source electrode/drain electrode, and the organic semiconductor layer is in contact with the source electrode/drain electrode on both sides, so the effect is particularly large.

The organic EL display device of the present invention is composed of a light-transmitting substrate, a light-transmitting electrode disposed on the light-transmitting substrate, an EL organic layer disposed on the light-transmitting electrode, and a laminated arrangement on the EL organic layer. The driving element, the switching element and the capacitor are composed of a stacked structure of the first conductive layer, the organic semiconductor layer, and the second conductive layer, at least on the side surface of the second conductive layer via an insulating layer. The vertical FET is formed with the pole electrode structure. Here, the EL organic layer refers to a part of the organic semiconductor layer stacked so as to form an organic EL part (a part where an electrode and an organic semiconductor layer are stacked so as to form a light emitting part). In addition, when the first conductive layer constituting the driving element is laminated with the organic EL part, it may be shared with the electrodes of the organic EL part, or may be replaced by the EL organic layer of the organic EL part.

It is also possible that the above-mentioned driving element is provided on the above-mentioned EL organic layer, and a part of the third conductive layer for the gate electrode formed on the upper surface of the driving element is used as one of the source electrode/drain electrode of the above-mentioned switching element. A vertical FET is formed by laminating an organic semiconductor layer and the other fourth conductive layer as a source electrode/drain electrode on a part of the third conductive layer, and the switching element is formed using the vertical FET. In addition, it is also possible that the above-mentioned driving element and the switching element are arranged on the above-mentioned EL organic layer and divided into a driving element area and a switching element area on a plane, and the above-mentioned switching element is an organic semiconductor layer for a switching element and an organic semiconductor of the above-mentioned driving element. A lateral FET in which layers are formed continuously or simultaneously, are in contact with the same surface of the organic semiconductor layer, and a pair of source electrodes/drain electrodes are provided separately.

As a specific structure, it can be formed as follows: On the above-mentioned EL organic layer, the first organic semiconductor layer for the above-mentioned driving element is provided, and a source electrode for the driving element is provided on a part of the first organic semiconductor layer. The second conductive layer of one side of the electrode/drain electrode is provided with a first insulating layer as a gate insulating film for the above-mentioned driving element on the exposed surface, and the above-mentioned driving element is provided on the first insulating layer. The gate electrode for use and the third conductive layer as one of the source electrode/drain electrode for the above-mentioned switching element, on the third conductive layer in the switching element region where the above-mentioned switching element is provided, the above-mentioned switch is provided. The second organic semiconductor layer for elements is provided with a fourth conductive layer as the other side of the source electrode/drain electrode for the switching element on a part of the second organic semiconductor layer, and the driving element is provided on the second organic semiconductor layer. On the above-mentioned third conductive layer in the driving element region, on the exposed part of the above-mentioned second organic semiconductor layer in the above-mentioned switching element region and on the above-mentioned fourth conductive layer, the dielectric layer of the capacitor and the The second insulating layer of the gate insulating film is provided with a fifth conductive layer serving as a gate electrode for the switching element on the second insulating layer in the switching element region, and a fifth conductive layer serving as a gate electrode for the switching element is provided on the second insulating layer in the driving element region. On the second insulating layer, a sixth conductive layer serving as an electrode of the capacitor is provided.

By forming this structure, the gate electrode of the driving element and the source electrode/drain electrode of the switching element can be continuously formed at the same time, and all elements can be formed only by sequential lamination, which can be formed by a very simple manufacturing process, and can The electrode of the capacitor is shared with the gate electrode of the drive element.

In addition, as another specific structure, it may be formed as follows: a third insulating layer is provided on the above-mentioned EL organic layer in the above-mentioned switching element region, and the above-mentioned EL in the above-mentioned driving element region is provided on the third insulating layer. On the organic layer, the first organic semiconductor layer for the above-mentioned drive element and the switch element is provided, and on a part of the first organic semiconductor layer in the above-mentioned drive element region, a source electrode/drain as the drive element is provided. The second conductive layer on the other side of the pole electrode, and on the first organic semiconductor layer in the above-mentioned switching element region, the seventh and eighth conductive layers serving as the source electrode and the drain electrode for the switching element are separately provided. layer, a first insulating layer as a gate insulating film for the driving element is provided on the exposed portion of the first organic semiconductor layer in the driving element region and the second conductive layer, and in the switching element region In the exposed portion of the above-mentioned first organic semiconductor layer and the above-mentioned seventh and eighth conductive layers, a gate electrode for the above-mentioned switching element is provided in such a manner that a part of any one of the above-mentioned seventh or eighth conductive layers is exposed. The fourth insulating layer of the insulating film is provided with a third conductive layer as a gate electrode for the driving element on the first insulating layer so as to be electrically connected to the exposed portion of the seventh or eighth conductive layer. , and on the fourth insulating layer, a fifth conductive layer serving as a gate electrode for the switching element is provided, and on the third conducting layer, a second insulating layer serving as a dielectric layer of the capacitor is provided. On the second insulating layer, a sixth conductive layer serving as an electrode of the capacitor is provided.

According to this structure, since the organic semiconductor layer for driving elements and the organic semiconductor layer for switching elements can be formed simultaneously and continuously, the formation process of the organic semiconductor layer which is a key step can be completed at one time. In this case, the switching element is a horizontal FET, and since the channel length of the switching element can be made small, the source electrode/drain electrode can be formed using a shadow mask.

Between the above-mentioned EL organic layer and the above-mentioned first organic semiconductor layer, an upper electrode of the organic EL part and a conductive layer as one of the source electrode/drain electrode of the above-mentioned drive element are provided as a common conductive layer or as a separate conductive layer. Conductive layer, thus, the current is diffused through the low-resistance first conductive layer, the current can be diffused to the whole organic EL display part, and the lower part of the switching element can also emit light, so that the whole can emit bright light, so it is preferable.

By forming the structure of the organic semiconductor element of the present invention, a channel region is formed on the side of the organic semiconductor layer, or on the organic semiconductor layer where the gate electrode near the side of the second conductive layer is opposite to the first conductive layer, because The channel length is determined by the thickness of the organic semiconductor layer, so the channel length can be controlled at the nanometer level with very high precision. Moreover, both the organic semiconductor layer and the source electrode/drain electrode are formed of a flat stacked structure, and there is no problem of coverage due to step difference. As a result, the contact resistance is reduced, and a FET having a desired channel length can be formed with precise dimensions. Therefore, transistor characteristics such as increase in drain current and decrease in operating voltage can be greatly improved.

In addition, since the gate electrode is formed above, for example, in the case of connecting the source/drain of the switching element to the gate electrode of the driving element of the display device, or connecting a capacitor to the gate of the driving element to form a control circuit In the case of , it can be easily formed by sequentially laminating layers on the upper side. In particular, if it is applied to an organic light emitting (EL) display device, it can be formed only by laminating together with the organic EL part (light emitting part).

As a result, although an organic semiconductor is used, a semiconductor device having a FET with a very short channel length can be obtained, and the channel length can be controlled by the film thickness of the organic semiconductor layer, so it is possible to form nanometer-scale FETs with very tight channel lengths can be used as driving elements for organic light-emitting (EL) display devices. Furthermore, since it can be formed with only a simple laminated structure, and since the channel portion is also formed in a self-integrated manner, the processing cost can be reduced and it can be obtained very cheaply.

In addition, by forming the structure of the organic EL display device of the present invention, even if the driving element does not use photolithography technology, a FET with a short channel length and a very low contact resistance can be obtained. The driving elements and capacitors are formed on the EL portion, and there is no need to arrange the driving elements and the like in parallel with the display portion. Therefore, most of the area of each pixel can be constituted by the organic EL portion. As a result, an organic EL display device having a greatly improved aperture ratio and capable of clear display can be obtained at very low cost. In addition, since the drive element has a vertical structure, the current flows in the vertical direction, so the current flows continuously through the organic EL portion. Therefore, there is no useless path, current can flow with low resistance, and even if there is no upper electrode of the organic EL part or source electrode/drain electrode on the lower side of the drive element, the current can flow from the drive element to the organic EL part. . As a result, a high-performance active-matrix organic light-emitting (EL) display device can be obtained at low cost, which greatly contributes to the new development of image display devices.

Description of drawings

FIG. 1 is an explanatory view showing a cross-sectional structure of an embodiment of an organic semiconductor element of the present invention.

2A to 2D are explanatory cross-sectional views showing the manufacturing process of the organic semiconductor element shown in FIG. 1 .

3A and 3B are cross-sectional explanatory views showing another embodiment of the organic semiconductor element of the present invention.

Fig. 4 is a cross-sectional explanatory view showing still another embodiment of the organic semiconductor element of the present invention.

5A to 5D are diagrams illustrating a schematic configuration of an embodiment of the organic EL display device of the present invention.

FIG. 6 is a diagram illustrating the structure of the organic EL unit in FIG. 1 .

7 is a cross-sectional explanatory view showing a specific structural example of the organic EL display device of the present invention.

8 is a cross-sectional explanatory view showing a specific structural example of the organic EL display device of the present invention.

9A to 9C are cross-sectional explanatory views of a conventional organic semiconductor element.

Symbol Description

1 Substrate

2 The first conductive layer

3 Organic semiconductor layer (first organic semiconductor layer)

4 Second conductive layer

5 insulation layer (first insulation layer)

6 Gate electrode (third conductive layer)

7 The second organic semiconductor layer

8 The fourth conductive layer

9 second insulating layer

10 The fifth conductive layer

11 The sixth conductive layer

12 third insulating layer

13 The seventh conductive layer

14 The eighth conductive layer

15 The fourth insulating layer

Detailed ways

Next, the organic semiconductor element of the present invention and an organic EL display device using the organic semiconductor element will be described with reference to the drawings. The organic semiconductor element of the present invention, as shown in the cross-sectional explanatory diagram of one embodiment thereof in FIG. On the conductive layer 2, the organic semiconductor layer 3 and the second conductive layer 4 serving as the other of the source electrode and the drain electrode are provided. In the example shown in FIG. 1 , the organic semiconductor layer 3 and the second conductive layer 4 are formed smaller than the first conductive layer 2 and have a structure in which a part of the first conductive layer 2 is exposed. On its surface, there is a FET formed by providing a gate electrode (third conductive layer) 6 via an insulating layer 5 as a gate insulating film. In addition, the substrate 1 is very thick compared with other layers, and the relationship of the thickness is not shown in the figures including the following figures.

The substrate 1 may be made of inorganic materials such as glass and alumina sintered body, various insulating plastics such as polyimide film, polyester film, polyethylene film, polyphenylene sulfide film, and parylene film, etc. These mixed materials of inorganic substances and organic substances, conductive substrates such as semiconductor substrates that also serve as the first conductive layer, etc., depending on the purpose, each film of the organic semiconductor element is laminated, as long as it has sufficient strength to maintain the device. When used as an organic EL display device described later, it means the entire substrate on which the organic light-emitting part is formed. When only an organic semiconductor element is produced, a lightweight and flexible organic TFT can be produced by using a plastic substrate.

As the first conductive layer 2 and the second conductive layer 4 of the source electrode/drain electrode, use a metal with excellent conductivity, good adhesion with the substrate and the organic semiconductor layer, and low contact resistance, or a conductive organic ( Inorganic) materials, or their complex materials. Specifically, in order to obtain ohmic contact with the p-type organic semiconductor layer, a metal having a large work function is preferable, and gold, platinum, or the like is preferably used. However, it is not limited to these materials. In addition, when the surface of the semiconductor layer is doped with a dopant at a high density, it is possible to make carriers form a tunnel between the metal and the semiconductor. Since it has nothing to do with the material of the metal, it can also be used as a gate electrode described later. Metal materials are listed as electrode materials. These conductive layers 2 and 4 are formed to have a thickness of about 20 to 200 nm, preferably about 50 to 100 nm, which can be used as a low resistance layer.

As the organic semiconductor layer 3, a material with a high on-off ratio, excellent carrier transport properties, and good adhesion to the insulating layer and electrode materials can be used, and π-electron conjugated aromatic compounds, chain compounds, organic compounds, etc. Pigments, organosilicon compounds, etc. Specifically, pentacene, tetracene, thiophene oligomer derivatives, phenylene derivatives, phthalocyanine compounds, polyacetylene derivatives, polythiophene derivatives, cyanine pigments, etc. can be used, but not limited to these materials. The organic semiconductor layer 3 is formed to have a thickness of about 50 to 5000 nm, preferably about 100 to 1000 nm, according to a desired channel length.

As the insulating layer 5 of the gate insulating film, polychloroprene, polyethylene terephthalate, polyoxymethylene, polyvinyl chloride, polyvinylidene fluoride, cyanoethyl pullulan, etc. Polysaccharide (cyano-ethylpullulan), polymethyl methacrylate, polysulfone, polycarbonate, polyimide and other organic materials. In addition, inorganic materials such as SiO ₂ , SiN _x , and Al ₂ O ₃ that can be used in a conventional pattern process can also be used. Of course, it is not limited to these materials, and two or more of these materials may be used together. The insulating layer 5 has excellent insulating properties, and is formed to have a thickness of about 10 to 1000 nm, preferably about 50 to 100 nm, in order to ensure a withstand voltage capable of withstanding a voltage that can be applied to the gate electrode.

As the gate electrode (third conductive layer) 6 , an organic material such as polyaniline or polythiophene, or a conductive ink that can be used by a coating method with a simple electrode formation process is preferable. In addition, metals such as gold, platinum, chromium, palladium, aluminum, indium, molybdenum, nickel, alloys of these metals, tin oxide, indium oxide, etc. , Indium tin oxide (ITO) and other inorganic materials. In addition, silicon, polysilicon, and amorphous silicon can also be used. In addition, these materials may be used in combination of two or more.

An example of a method of manufacturing the organic semiconductor will be described with a specific example with reference to the process diagrams shown in FIGS. 2A to 2D . First, as shown in FIG. 2A , the first conductive layer 2 as one of the source electrode and the drain electrode is formed by a vacuum evaporation method or the like. The first conductive layer 2 can also be formed of a conductive organic material or the like by a coating method, for example. Next, a shadow mask is set, and as shown in FIG. 2B , the organic semiconductor layer 3 is formed so that a part of the first conductive layer 2 is exposed. Next, using the same mask, as shown in FIG. 2C , the second conductive layer 4 serving as the other source electrode/drain electrode is formed on the organic semiconductor layer 3 . Thereafter, insulating layer 5 is formed on the entire surface. Then, gate electrode 6 is formed on the surface thereof. As a result, a FET having the cross-sectional structure shown in FIG. 1 was formed. In addition, in the above method, each layer is formed by a vacuum deposition method, but it may also be formed by a coating method.

According to the organic semiconductor element of the present invention, the organic semiconductor layer 3 sandwiched between the first and second conductive layers 2, 4 as the source electrode/drain electrode is located on the side of the insulating layer 5, A gate electrode 6 is formed. Therefore, the side surface of the organic semiconductor layer 3 facing the gate electrode 6 of the organic semiconductor layer 3 becomes a channel region, and the channel is turned on-off by the control of the gate electrode 6 to perform FET operation.

In this structure, the interface between the organic semiconductor layer 3 and either of the first and second conductive layers 2, 4 serving as source/drain electrodes is flat and has good adhesion, so the contact resistance is very low. In addition, since the insulating layer 5 and the gate electrode 6 are formed at the step difference between the organic semiconductor layer 3 and the first conductive layer 2, the coverage is deteriorated, and there is a possibility that the insulating layer is not fully filled at the corner, but since the insulating layer is inherently insulating No current flows through layer 5, so contact resistance is not a problem.

Furthermore, since the channel length is determined by the thickness of the organic semiconductor layer 3, a desired channel length can be formed by controlling the film formation thickness. The thickness of the organic semiconductor layer 3 can be formed on the order of nanometers, and the length of the channel can also be controlled to this order. In addition, since a simple stacked structure is used and the channel part can be processed in a self-integrated manner, the manufacturing is simple and the processing cost can be greatly reduced. As a result, a large drain current can be obtained with a relatively low operating voltage, and a high-performance FET can be obtained at low cost. Therefore, it can be sufficiently used as a driving element of a current-driven organic light-emitting display device, and the organic EL display device can be constituted by continuous lamination with the organic EL part.

In the structures shown in FIGS. 1 and 2A to 2D, the organic semiconductor layer 3 and the second conductive layer 4 are formed in a partially vacant manner, and the gate electrode is formed on the side of the insulating layer, but it is not necessarily such a structure. It is formed as The configurations of the modified examples shown in FIGS. 3A to 3B can similarly perform FET operation with the thickness of the organic semiconductor layer 3 as the channel length.

That is, in the structure shown in FIG. 3A, the first conductive layer 2 is not formed on the entire surface, but is formed in a partially vacant shape. According to this structure, since the gate electrode 6 is more completely opposed to the side surface of the organic semiconductor layer 3 , so the on-off of the channel region can be controlled with a low gate voltage. In addition, other parts are the same as the example shown in FIG. 1, and the same symbols are used for the same parts, and description thereof will be omitted.

In addition, on the contrary, in the structure shown in FIG. 3B, the organic semiconductor layer is provided on the entire surface, and only the second conductive layer 4 is formed in a state of vacant part. Layer 5 is provided with a gate electrode 6 . In this structure, the organic semiconductor layer 3 near the side surface of the second conductive layer 4 serves as a channel region, which can be controlled on and off by the gate electrode 6 . In this example, other parts are the same as the example shown in FIG. 1, and the same parts are given the same symbols, and their descriptions are omitted. With this structure, only the second conductive layer 4 needs to be patterned when a plurality of driving elements are formed side by side, and thus there is an advantage that the manufacturing process is simple.

Fig. 4 is an explanatory cross-sectional view similar to Fig. 1 showing another embodiment of the organic semiconductor device of the present invention, in which injection and extraction of drain current are further improved. That is, source/drain layers (carrier injection layers) 3 a and 3 b are formed on the interfaces between the organic semiconductor layer 3 and the first conductive layer 2 and the second conductive layer 4 . The source/drain layers 3a, 3b are organic semiconductor layers that reduce the energy barrier between the source/drain electrodes 2, 4 and the organic semiconductor layer 3, by making the organic semiconductor layer 3 and the source electrode/ The energy barrier between the drain electrodes 2 and 4 becomes smaller, the injection and extraction of carriers become easier, lower contact resistance can be obtained, and a larger drain current can be easily obtained with a lower driving voltage.

The organic FET of the present invention has a structure in which the source/drain electrodes 2 and 4 are provided on the upper and lower surfaces of the organic semiconductor layer 3, so by providing the source layer at both ends of the channel region through which current can easily flow The /drain layers 3a and 3b can obtain an effect equivalent to that of making the source region/drain region have a high impurity concentration in a silicon-based semiconductor layer so that current can easily flow. That is, in the conventional structure in which the source electrode/drain electrode is provided on one side of the organic semiconductor layer, since the current path is lateral to the surface side of the organic semiconductor layer, it is difficult to provide the source/drain electrode except for the channel region. However, in the present invention, the source/drain layers 3a, 3b are easily provided because of the simple stacked structure.

As the source/drain layers (carrier injection layers) 3a, 3b, for example, CuPc (copper phthalocyanine), PANI (polyaniline), PEDOT (poly-3,4-ethylenedioxythiophene) or the like can be used.

5A to 5C are diagrams showing a schematic configuration of an organic EL display device of the present invention using the above-mentioned FET. That is, the organic EL display device of the present invention is characterized in that a light-transmitting electrode 21 is provided on a light-transmitting substrate 1a, an organic EL portion 20 is provided on the light-transmitting electrode 21, and an organic EL portion 20 is provided on the light-transmitting electrode 21. Above, the driving element Tr ₁ , the switching element Tr ₂ and the capacitor C are respectively stacked on the organic EL portion 20 , and the driving element Tr ₁ is constituted by the vertical FET having the above-mentioned structure. That is, in order to display a fine image with this kind of display device, as shown in the equivalent circuit diagram _of one pixel in FIG. The Tr ₂ is connected to the gate of the drive element Tr ₁ , and forms a matrix with word lines WL and bit lines BL, so that each pixel can be selected as an active type.

In the present invention, an organic FET having the above-mentioned structure is used as the driving element Tr ₁ , so that an FET with a short channel length can be formed using an organic semiconductor without using photolithography, and can be stacked on the organic EL unit 20 . Therefore, as shown in the plan explanatory diagram of one pixel in FIG. 5C, substantially the entire surface of the pixel can be used as the light emitting portion L, and there is no need to ensure the area of the conventional transistor Tr and capacitor CAPA shown in FIG. 5D. Compared with the structure, the area of the light emitting part L can be greatly increased.

As the substrate 1a, since light is obtained from the substrate side, a translucent glass substrate or plastic film is used. In addition, as the translucent electrode 21, ITO (Indium Tin Oxide: indium tin oxide), indium oxide, or the like provided by a vacuum evaporation method, a sputtering method, or the like is used.

The organic EL part 20, for example, as shown in FIG. 6, is provided with an EL organic layer 27 made of a hole transport layer 23, a light emitting layer 24, and an electron transport layer 25, for example, on a light-transmitting electrode 21 on a glass substrate Sub 1a, On top of it, another electrode (upper electrode) 26 is sequentially laminated, and the EL organic layer 27 is not limited to the three-layer structure, as long as at least a light-emitting layer is formed, and each layer may be further multi-layered.

Generally, in order to improve the hole injection into the light-emitting layer 24 and the stable transport of holes, it is required that the ionization energy of the hole-transport layer 23 be small enough to block the electrons (energy barrier) to the light-emitting layer 24, which can be used Amine materials, such as triphenyldiamine derivatives, styrylamine derivatives, amine derivatives having aromatic condensed rings, etc., have a thickness of 10-100 nm, preferably 20-50 nm. In addition, although not shown in the figure, a hole injection layer is provided between the hole transport layer 23 and the anode electrode 21 to further improve the injectability of carriers into the hole transport layer 23 . In this case, in order to improve the hole injection property from the anode electrode 21 , a material with good ionization energy matching is used, and as a representative example, amines or phthalocyanines can be used. In the example shown in FIG. 6 , as the hole transport layer 23 , NPB was set to a thickness of 35 nm.

The light-emitting layer 24 is selected according to the light-emitting wavelength, but by using Alq3 as a base material and doping an organic fluorescent material, the light-emitting color inherent to the doped material can be obtained, and the light-emitting efficiency and stability can be improved. This doping is carried out at about several weight (wt) % (0.1 to 20 wt %) for the luminescent material.

As the fluorescent substance, quinacridone, rubrene, styryl dyes and the like can be used. In addition, quinoline derivatives, tetraphenylbutadiene, anthracene, perylene, hexabenzocene, 12-phthaloperinone derivatives, phenylanthracene derivatives, tetraarylethene Derivatives etc. In addition, it is preferably used in combination with a host material capable of emitting light by itself. As a host material, a quinolinolate (quinolinolate) complex is preferred, and 8-hydroxyquinoline (quinolinol) or its derivatives are preferably used as a ligand. As aluminum complexes, phenylanthracene derivatives, tetraarylethene derivatives, and the like can be used.

The electron transport layer 25 has the function of improving the injectability of electrons from the cathode 26 and the function of stably transporting electrons, so in the example shown in FIG. quinolinolate)aluminum)) is set to a thickness of around 25nm. If this layer becomes too thick, the series resistance component will increase, so it should not be too thick, and it is usually set to a thickness of about 10 to 80 nm, preferably about 20 to 50 nm. As the electron transport layer 25, in addition to the above-mentioned materials, quinoline derivatives, metal complexes using 8-quinolinol or its derivatives as ligands, phenylanthracene derivatives, tetraaryl Vinyl derivatives, etc. When the gap between the electron transport layer 25 and the cathode electrode 26 is large, an electron injection layer 26 a made of LiF or the like is provided in the same manner as on the hole side.

As the cathode electrode 26 , in order to improve the electron injection property, a metal having a small work function is mainly used. As typical examples, Mg, K, Li, Na, Ca, Sr, Ba, Al, Ag, In, Sn, Zn, Zr, etc. are generally used. In addition, a translucent conductive film such as indium oxide can also be used. In order to prevent and stabilize these metals from oxidation, they are often alloyed with other metals. In the example shown in FIG. 6 , an Al layer of about 110 nm is formed via a LiF layer 26 a to form a cathode electrode 26 .

Since the drive element _Tr1 is connected in series with the organic EL unit 20 , as the channel length becomes longer, the resistance increases and the current supplied to the organic EL unit 20 decreases. Therefore, an FET with a short channel length is preferable, and a vertical organic FET having the structure shown in the above-mentioned FIG. 1 or FIGS. 3A to 3B can be used. Since this FET is a vertical type, even without the first conductive layer 2 as the source electrode/drain electrode shown in FIG. 1 or FIGS. Electric current may also flow directly through the organic EL section 20 to cause it to emit light. However, by providing the first conductive layer that shares the electrodes of both, the current passing through the drive element _Tr1 is diffused over the entire surface by the first conductive layer, so that the current can be supplied to the entire organic EL section 20. Light emitting over the area is therefore preferred.

On the other hand, since the switching element Tr ₂ does not require much current, it is possible to use the organic FET with the structure shown in FIG. 1 or FIGS. structure of the FET. The capacitor C is used to keep the driving element turned on for a certain period of time, and has a capacitance capable of holding data.

Next, it will be further described in detail using a specific structural example. FIG. 7 shows an example in which the organic FET with the above-mentioned vertical structure is used for both the driving element _Tr1 and the switching element _Tr2 . That is, a light-transmitting electrode 21 made of, for example, ITO is formed on a light-transmitting substrate 1a such as glass, and an organic EL unit 20 having the structure shown in FIG. 6 is laminated. Then, on the surface thereof, the first conductive layer 2 shared with one of the upper electrode of the organic EL part and the source electrode/drain electrode of the drive element is formed. In addition, as mentioned above, the first conductive layer 2 may not be present. The organic semiconductor layer 3 is stacked on the drive element region A on the surface, and the second conductive layer 4 as the source electrode/drain electrode is provided on a part (two places in FIG. 7 ) of the surface. , the first insulating layer 5 as a gate insulating film is provided on the entire surface thereof, and the third conductive layer 6 as a gate electrode is provided on the surface thereof, thereby, as a driving element Tr ₁ , an organic organic film having the above-mentioned structure is formed. FET.

In the switching element region B, the third conductive layer 6 is used as one of the source electrode and the drain electrode, and the second organic semiconductor layer 7 for the switching element is laminated on the surface thereof, and a part of the surface is provided as the source electrode. On the surface of the fourth conductive layer 8 on the other side of the electrode/drain electrode and the third conductive layer 6 in the drive element region A, a second insulating layer as a gate insulating film for switching elements and an insulating film for capacitors is provided. 9. Then, using the same material, a fifth conductive layer 10 serving as a gate electrode for switching elements is formed on the second insulating layer 9 in the switching element region B, and a fifth conductive layer 10 as a gate electrode for the switching element is formed on the second insulating layer in the driving element region A. The sixth conductive layer 11 of the capacitor electrode. Then, by forming a protective film 19 (see FIG. 5A ) on the surface, an organic light emitting display device having a structure shown in the schematic diagram of FIG. 5A is obtained.

In this structure, on the first organic semiconductor layer 3 of the portion D of the side end portion of the second conductive layer 4 opposite to the first conductive layer 2, the channel region of the drive element _Tr1 is formed, and when the channel is turned on, The current flows in the vertical direction in the portion D, and the current flows through the organic EL portion 20 below it to emit light. Therefore, reducing the width of the second conductive layer 4 as much as possible and forming multiple ones can increase the number of channel regions, increase the channel width, and facilitate more current to flow, so it is preferable. In addition, it is preferable to form the strip-shaped second conductive layer 4 continuously in a direction perpendicular to the paper surface.

In the example shown in Fig. 7, two second conductive layers 4 are formed. , then the size of each of R, G, and B of a pixel is 100 μm×300 μm, and more second conductive layers 4 can be formed (continuously formed in a strip shape in the direction of 300 μm or in the direction of 100 μm).

In the example shown in FIG. 7, the driving element Tr ₁ is not formed on the lower side of the switching element Tr ₂ , but since the third conductive layer 6 is the uppermost part of the driving element Tr ₁ , the height becomes slightly higher, and the driving element Tr 1 can be formed on the lower side of the switching element Tr 1. The switching element Tr ₂ is formed on the basis of the element Tr ₁ , and as shown in FIG. 7 , it is not necessary to separate the driving element region A and the switching element region B in a plane.

In addition, the example shown in FIG. 7 is a structure in which the first organic semiconductor layer 3 and the first conductive layer 2 are provided on substantially the entire surface of the drive element region (the structure of the organic semiconductor element shown in FIG. 3B described above), but in In the structure of the organic semiconductor element shown in FIG. 1 or FIG. 3A described above, a vertical FET can also be formed, and the first organic semiconductor layer 3 or the first conductive layer 2 can be formed in accordance with the pattern of the second conductive layer 4 .

In addition, in the example shown in FIG. 7, the switching element Tr ₂ is also a FET with a vertical structure, and like the example of the driving element Tr ₁ , on the second organic semiconductor layer 7 in the vicinity of the side end of the fourth conductive layer 8 A channel region is formed, but the switching element Tr ₂ does not require current so much, and only a fourth conductive layer 8 can be formed, and a driving element can be formed on the rear side (direction perpendicular to the paper). In this way, the driving element Tr ₁ is formed on substantially the entire surface of the pixel, and current can be directly supplied from the driving element Tr ₁ to substantially the entire surface of the organic EL part 20. Therefore, even if the first conductive layer 2 is not present, the operation will not be hindered. .

FIG. 8 shows an example in which the switching element _Tr2 is formed using a conventional horizontal-structure FET instead of the above-mentioned vertical-structure FET. Since the switching element _Tr2 does not require so much current, no problem arises even if the channel length is not short. Therefore, there is no hindrance to the FET of the conventional structure using the shadow mask. In the example shown in FIG. 8, up to the first conductive layer 2 is the same as the example shown in FIG. 7. After the first conductive layer 2 is formed, a third insulating layer 12 is provided in the switching element region B. On layer 12 and the first conductive layer 2 in the driving element region A, the first organic semiconductor layer 3 for driving elements and switching elements is stacked, and on it, in the driving element region A, the second conductive layer 3 is formed in the same manner as above. layer 4, and at the same time, in the switching element region B, the seventh and eighth conductive layers 13, 13, 14.

Then, an insulating film is formed so that a part of, for example, a part of the eighth conductive layer 14 as one of the source electrode/drain electrode for the switching element is exposed, and the first insulating layer 5 as the gate insulating film for the driving element and the first insulating layer 5 as the gate insulating film for the driving element are provided. The fourth insulating layer 15 is a gate insulating film for switching elements. In addition, the first insulating layer 5 and the fourth insulating layer 15 may be formed continuously, but they are formed in such a manner that a part of the eighth conductive layer 14 is exposed. Then, on the first insulating layer 5 in the driving element region A, the third conductive layer 6 serving as the gate electrode for the driving element is provided in such a manner as to be in contact with the eighth conductive layer 14, and on the fourth insulating layer 5 in the switching element region B, Between the source/drain electrodes 13 and 14 on the layer 15, the fifth conductive layer 10 is provided as a gate electrode for switching elements. On the third conductive layer 6 in the driving element region A, a sixth conductive layer 11 serving as a capacitor electrode is further provided via the second insulating layer 9 , thereby forming an organic light emitting display device. In addition, in FIG. 8 , the parts corresponding to those in FIG. 7 are assigned the same symbols as those in FIG. 7 .

In this structure, the driving element is the same as the structure shown in FIG. 7, but the FET of the switching element is formed in a lateral type, so it is characterized in that the organic semiconductor layers of the two elements are simultaneously formed on one layer of the first organic semiconductor layer 3. . However, in the above-mentioned structure shown in FIG. 7, one of the gate electrode of the driving element and the source electrode/drain electrode of the switching element is formed on the third conductive layer 6 at the same time. However, in the structure shown in FIG. In this case, since both the source electrode/drain electrodes 13 and 14 of the switching element Tr ₂ are formed simultaneously with the other 4 of the source electrode/drain electrode of the driving element Tr ₁ , the source electrode/drain electrode 14 of the switching element Tr 1 are formed at the same time. The other side 14 of the drain electrode is in contact with each other to form the gate electrode 6 of the driving element. According to this structure, there are advantages in that the organic semiconductor layer 3 of two elements can be formed simultaneously in the same layer as a key, and that the number of manufacturing steps can be reduced. Of course, they may not be formed simultaneously on the same layer.

In the example shown in FIG. 8 , the organic semiconductor layer for the driving element and the organic semiconductor layer for the switching element are continuously formed on one layer, but they may also be formed separately. However, they can be formed using the same material at the same time, and can be formed in one process. In addition, in the structure shown in FIG. 8, the seventh and eighth conductive layers 13, 14 serving as source electrodes/drain electrodes for switching elements are formed on the upper side of the first organic semiconductor layer 3, but they may be formed on the organic semiconductor layer 3. The lower side of the semiconductor layer 3 is formed, and the seventh and eighth conductive layers 13, 14 as source electrodes/drain electrodes can be formed on the upper side of the organic semiconductor layer 3, and the seventh and eighth conductive layers 13, 14 can be formed on the lower side of the organic semiconductor layer 3 as The fifth conductive layer 10 of the gate electrode.

As shown in FIG. 7 and FIG. 8, according to the organic EL display device of the present invention, since the FET for the driving element is provided on the organic EL portion, it is possible to share the connection between the organic EL portion and the driving element. electrode, or both electrodes can be omitted. In addition, since the capacitor is also formed on the gate electrode of the driving element, both electrodes can be shared. In addition, the switching elements are also laminated on the gate electrodes of the driving elements, or formed simultaneously with the layers of the driving elements, so an active matrix organic light-emitting display device can be obtained through simple lamination.

Furthermore, since the driving elements, switching elements, and capacitors are all formed on the organic EL portion, the area of the display portion is not reduced by the driving elements, etc., and the aperture ratio can be greatly increased. In addition, since the organic EL part is formed on the ITO electrode on the light-emitting surface side first, the resistance of the light-transmitting electrode can be sufficiently reduced, and the luminous efficiency can be improved.

Industrial availability

The organic semiconductor element of the present invention can be used in integrated circuits of electronic equipment such as portable displays and electronic labels such as electronic price tags and electronic goods tags, which are provided at low prices. In addition, the organic EL display device of the present invention can be used in mobile phones. , portable terminals, thin TVs, etc.

Claims (12)

1. organic semiconductor device is characterized in that:

Have FET, described FET comprises: substrate; Be arranged on first conductive layer on this substrate as a side of source electrode/drain electrode; Be arranged on the organic semiconductor layer on this first conductive layer; Be arranged on second conductive layer on this organic semiconductor layer as the opposing party of source electrode/drain electrode; In the side of described organic semiconductor layer or remove the part of described second conductive layer and the surface of the described organic semiconductor layer that exposes and the side of described second conductive layer, the gate electrode that is provided with across insulating barrier.

2. organic semiconductor device as claimed in claim 1 is characterized in that:

Between described first conductive layer and organic semiconductor layer, and/or between described second conductive layer and described organic semiconductor layer, be provided with the organic semiconductor layer that reduces energy barrier.

3. organic semiconductor device as claimed in claim 1 is characterized in that:

Described first conductive layer is provided with in wide scope, the mode that described organic semiconductor layer and described second conductive layer expose with side alignment separately is arranged on this first conductive layer, mode with the side that covers this organic semiconductor layer and second conductive layer is provided with described gate electrode across described insulating barrier.

4. organic semiconductor device as claimed in claim 1 is characterized in that:

The mode that described first conductive layer, described organic semiconductor layer and described second conductive layer expose with side alignment separately is provided with, mode with the side that covers this first conductive layer, organic semiconductor layer and second conductive layer is provided with described gate electrode across described insulating barrier.

5. organic semiconductor device as claimed in claim 1 is characterized in that:

Described first conductive layer and described organic semiconductor layer are provided with in wide scope, described second conductive layer is arranged on this organic semiconductor layer in the mode of exposing its side, mode with the side that covers this second conductive layer is provided with described gate electrode across described insulating barrier.

6. organic EL display is characterized in that:

By light-transmitting substrate, be arranged on optically transparent electrode on this light-transmitting substrate, be arranged on the EL organic layer on this optically transparent electrode and constitute at driving element, switch element and the capacitor of this EL organic layer superimposed layer setting, described driving element is provided with the longitudinal type FET formation of the structure of gate electrode at least by in the laminated construction of first conductive layer, organic semiconductor layer and second conductive layer across insulating barrier on the side of described second conductive layer.

7. the organic EL display of the FET of structure as claimed in claim 6 is characterized in that:

Between described EL organic layer and described driving element, be provided with the upper electrode of organic EL portion and as a side's of the source electrode/drain electrode of described driving element conductive layer, as common conductive layer or as separately conductive layer.

8. organic EL display as claimed in claim 6 is characterized in that:

Described driving element is arranged on the described EL organic layer, the part of the 3rd conductive layer that will use at this gate electrode that forms above driving element is as a side of the source electrode/drain electrode of described switch element, at a part of superimposed layer organic semiconductor layer of the 3rd conductive layer with as the opposing party's of source electrode/drain electrode the 4th conductive layer, form longitudinal type FET thus, utilize this longitudinal type FET to form described switch element.

9. organic EL display as claimed in claim 6 is characterized in that:

Described driving element and switch element, on described EL organic layer, be divided into driving element zone and switch element zone in the plane and be provided with, described switch element is a switch element with the horizontal type FET that organic semiconductor layer forms continuously or simultaneously with the organic semiconductor layer of described driving element, contacts with the identical faces of this organic semiconductor layer, a pair of source electrode/drain electrode branch is arranged.

10. organic EL display as claimed in claim 8 is characterized in that:

On described EL organic layer, be provided with first organic semiconductor layer that described driving element is used, part on this first organic semiconductor layer is provided with as second conductive layer of driving element with a side of source electrode/drain electrode, on the surface of exposing, be provided with first insulating barrier of the gate insulating film of using as described driving element, on this first insulating barrier, one side's of the source electrode/drain electrode that is provided with gate electrode that described driving element uses and uses as described switch element the 3rd conductive layer, on the 3rd conductive layer in being provided with the switch element zone of described switch element, be provided with second organic semiconductor layer that described switch element is used, part on this second organic semiconductor layer is provided with the opposing party's of source electrode/drain electrode of using as described switch element the 4th conductive layer, on described the 3rd conductive layer in being provided with the driving element zone of described driving element, on the exposed division of described second organic semiconductor layer in the described switch element zone and described the 4th conductive layer, second insulating barrier of the gate insulating film that is provided with the dielectric layer of described capacitor and uses as described switch element, on this second insulating barrier in described switch element zone, be provided with the 5th conductive layer of the gate electrode of using as described switch element, on described second insulating barrier in described driving element zone, be provided with the 6th conductive layer as the electrode of described capacitor.

11. organic EL display as claimed in claim 9 is characterized in that:

Described EL organic layer in the described switch element zone is provided with the 3rd insulating barrier, on the 3rd insulating barrier and on the described EL organic layer in the described driving element zone, be provided with first organic semiconductor layer that described driving element is used and switch element is used, on the part on this first organic semiconductor layer in described driving element zone, be provided with as second conductive layer of driving element with the opposing party of source electrode/drain electrode, and on described first organic semiconductor layer in described switch element zone, separately be provided with the source electrode used as described switch element and the 7th and the 8th conductive layer of drain electrode, on the exposed division of described first organic semiconductor layer in described driving element zone and described second conductive layer, be provided with first insulating barrier of the gate insulating film of using as described driving element, and on the exposed division of described first organic semiconductor layer in described switch element zone and the described the 7th and the 8th conductive layer, with the described the 7th or the mode exposed of the either party's of the 8th conductive layer a part, be provided with the 4th insulating barrier of the gate insulating film of using as described switch element, on described first insulating barrier, in the mode that is electrically connected with the described the 7th or the exposed division of the 8th conductive layer, be provided with the 3rd conductive layer of the gate electrode of using as described driving element, and on described the 4th insulating barrier, be provided with the 5th conductive layer of the gate electrode of using as described switch element, on described the 3rd conductive layer, be provided with second insulating barrier as the dielectric layer of described capacitor, on this second insulating barrier, be provided with the 6th conductive layer as the electrode of described capacitor.

12., it is characterized in that as claim 10 or 11 described organic EL displays:

Between described EL organic layer and described first organic semiconductor layer, be provided with the upper electrode of organic EL portion and as a side's of the source electrode/drain electrode of described driving element conductive layer, as common conductive layer or conductive layer separately.

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